1. Field of the Invention
The present invention relates in general to a safety securing system for an operation lever, and more particularly, to a safety securing system for preventing the operation of work equipments at the release of a security lever while an operation lever for controlling the construction machine of a construction vehicle is in operation.
2. Description of the Related Art
In general, a construction vehicle including an excavator has an operational lever like a joystick or a driving pedal. The joystick is used to operate working tools such as boom, arm, bucket, and swing unit. The driving pedal is used to accelerate the vehicle.
Hydraulic pressure from an engine-driven hydraulic pump is a driving power source of operations of the work equipment, the swing equipment, and the driving equipment. A controller controls every kind of control valves according to the control input (manipulated variable) of the operation lever and basically controls hydraulic pressure supplied to the work equipment and direction and flow of hydraulic fluid to operate the work equipment.
For instance, the excavator is heavy, massive construction equipment and is operated by hydraulic pressure, so it is very important to secure the safety during work. Usually, a safety lever is used to prevent the work equipment from operating unexpectedly. In a way to secure the safety, therefore, the work equipment operates only when the safety lever is released, and if the safety lever is locked out during the operation of the work equipment, the operation lever stops working and all work equipments also stop their operation.
However, if the safety lever is released when the operation lever is still in operation, there is always a possibility that the work equipment might operate at the same time of the release of the safety lever. In other words, although the safety lever is supposed to stop the work equipment during emergency and functions as a safety securing system, ensuring the work equipment to stop operation, it does not have a function of preventing the malfunction of the equipment when the safety lever is released with the operation lever being in operation.
As an attempt to solve the above problem, there was a technique for determining an operational state of the operation lever on the basis of a signal from a pressure sensor connected to the hydraulic fluid line of the operation lever, and stopping the engine of the excavator if the operation lever is in operation before the engine starts.
According to this technique, even though the operation lever is in operation while the safety lever is released, a controller, after determining the state of the operation lever, is capable of making the engine stop. Therefore, the mechanic malfunction where the work equipment suddenly starts operating as soon as the engine starts running does not occur any more. However, if a driver accidentally released the safety lever while the operation lever had been in operation after the engine started running, there is always a possibility that the work equipment would operate all of a sudden, causing an accident.